Holy Light, Ice, Death, and Law. Any of these four major fields were enough to take an entire lifetime to research.
Everyone would be naturally talented in different areas. A so-called genius in all areas would typically never reach the top in any area. The deeper the field of study, the more time would be needed to accumulate understanding. While longer-lived species could use their longer lifespans to accumulate more understanding, the short-lived humans didn't have such excellent conditions.
Roland's path for ability growth had been quite unique. He had reached the peak in all four areas. This seemed to break a maxim, but he actually wasn't multitasking at all.
Rather than treating each of these fields as a type of power and knowledge, Roland viewed them all more like philosophical ways of thinking.